JP2007502516A - High pressure discharge lamp - Google Patents

Abstract

The high-pressure discharge lamp comprises a discharge vessel (10) in which a discharge space (11) containing an ionizable filling material is enclosed. The discharge vessel has first and second necks (2, 3) facing each other and provided with a pair of electrodes (6, 7) arranged in the discharge space (13). . Each electrode has a tubular shape over its entire length. Preferably, the electrode does not have a coil in the discharge space. Preferably, the electrode extends to the outside of the discharge vessel. The high-pressure discharge lamp according to the present invention is relatively easy to manufacture.

Description

  The present invention relates to a high pressure discharge lamp.

  High pressure discharge lamps have become the mainstream lamp in lighting equipment retail applications, road lighting, city landscape beautification, beamers and projection televisions. There is a trend to create good conditions for range expansion. The end users of the market are increasingly interested in light homogeneity and prefer to use high pressure discharge lamps instead of halogen lamps for accent lighting because of higher luminous efficiency.

  In general, high pressure discharge lamps of the kind described in the opening paragraph have a discharge vessel with a high temperature resistant ceramic wall or a discharge vessel made of quartz glass. Such high-pressure discharge lamps are widely used in practice and have both high luminous efficiency and favorable color characteristics. The discharge vessel of the lamp contains one or more types of metal halides, and may or may not be accompanied by mercury and a filling noble gas for use as a start-up promoting gas.

In general, the filling material of the discharge vessel contains one or more types of metal iodides. The one or more metal iodides are derived, for example, from an alkali or rare earth group, if necessary combined with Tl, Cs, Na, Ca, etc., so that the overall color rendering coefficient CRI and color temperature T The desired value of _c is realized. In the present specification and claims, the rare earth metals are understood to mean the elements Sc, Y and lanthanoids.

In the present specification and claims, the ceramic wall of the discharge vessel refers to a single crystal metal oxide (for example, sapphire), a semi-transparent high density sintered polycrystalline metal oxide (for example, Al ₂ O ₃ , YAG), And a wall made from one material of translucent dense sintered polycrystalline metal nitride (eg, AlN).

  One high-pressure discharge lamp as described in the opening paragraph is known from US Pat. No. 2,951,171. This known discharge lamp comprises a translucent tube vessel, an inert filling gas, and a pair of conductive electrodes arranged in the tube vessel in an axially spaced manner. I have. Each electrode has a conical depression and an axial cylindrical recess filled with a material having a high electron-emitting property. The electrode is provided with a metal wire in the form of a spiral coil that is in contact with the wall of the recess.

  One drawback of the known high-pressure discharge lamp is that it is relatively difficult to manufacture the electrodes in the discharge lamp.

  The present invention has the object of completely or partially eliminating this drawback.

For the above purpose, according to the invention, a high-pressure discharge lamp as described in the opening paragraph is
It is assumed to have a discharge vessel enclosing a discharge space containing an ionizable filling material,
The discharge vessel is provided with a pair of electrodes arranged in the discharge space and having first and second necks facing each other;
Each of these electrodes is tubular throughout its length.

  It has been surprisingly observed that the start-up behavior of the discharge lamp is advantageously improved by using an electrode that is tubular throughout its length. The start-up of the high-pressure discharge lamp according to the invention causes an ignition at the tip of the tubular electrode. Known discharge lamp ignitions initiate an arc at any point on the electrode. The arc is usually connected to an electrode portion remote from the electrode tip. As the temperature in the known discharge lamp increases, the arc gradually moves to the tip of the electrode. This movement results in undesirable electrode sputtering and reduces the luminous flux maintenance factor and / or lifetime of known discharge lamps.

  In the high-pressure discharge lamp according to the present invention, the arc extends from the hole of the tubular electrode to the hole at the time of ignition. Sputtering is reduced and the effects of glow-arc transitions are minimized. Without intending to follow any particular theory, it is believed that the pores in the tubular electrode according to the present invention function as a cathode. In addition, it is considered that the hole size of the tubular electrode determines the cathode function of the high-pressure discharge lamp according to the present invention, and the wall thickness of the tubular electrode determines the anode function of the high-pressure discharge lamp.

  Preferably, the tubular electrode is made of tungsten. In principle, an additive such as Y, Rh, Dy or Ce is not necessary for the discharge lamp according to the present invention to exhibit good performance. The temperature of the discharge lamp with a tubular electrode essentially made of tungsten can be satisfactorily controlled. In addition, the operating temperature of a discharge lamp having a tubular electrode made of pure tungsten is about 100 degrees Celsius lower than the operating temperature of known discharge lamps. In the discharge lamp according to the invention, considerable cost savings are realized since the addition of relatively expensive additives to the tungsten electrode is no longer necessary and no further coils are required. Preferably, the tubular electrode is made by extrusion and sintering of tungsten.

  In known high-pressure discharge lamps, it is difficult to control the thermal contact between the coil and the electrode, making it relatively difficult to manufacture the electrode. In addition, the position of the coil relative to the electrode tip is also difficult to control. In particular, the wire end of the coil affects the behavior of the electrode. If the wire end protrudes from the electrode, the arc connects to the protruding portion, and the coil wire reaches a high temperature and melts so as to flow backward. In addition, during the life of a known discharge lamp, the coil may fuse to the electrode, thereby shifting the electrode behavior to an undesirable temperature range. This leads to known (early) defects or significant performance degradation of the known discharge lamp. For this reason, one advantageous embodiment of the high-pressure discharge lamp according to the invention is characterized in that the electrode does not have a coil in the discharge space.

  One preferred embodiment of the high-pressure discharge lamp according to the invention is characterized in that the electrodes extend to the outside of the discharge vessel. This facilitates the manufacture of the discharge lamp according to the invention. Preferably, the electrodes are partially filled by rods coupled to the opposite side of the electrodes from the discharge space. This solid rod allows electrical connection and adjusts the temperature profile of the electrode. Preferably, the rod extends into the discharge space. One advantage of a solid rod that exits the electrode and reaches into the discharge space is that if the electrode dimensions are the same, the heavier electrode is formed with a lighter tip and minimal heat loss at start-up Therefore, the ignition still occurs from the tip of the tubular electrode, and the arc is prevented from moving back to the undesired position by moving to the tip of the protruding rod.

の範囲内にあることを特徴とする。壁部または孔のいずれかが、陰極として作用する。一例として、１０００μｍの直径を有し、３５０μｍの内径を有する管状電極は、適切な壁部の厚さとして、３５０μｍを有する。内径が１００μｍの場合は、壁部の厚さは４５０μｍである。内径が８００μｍの場合は、壁部の厚さは１００μｍである。 The novel design of the electrodes in the high-pressure discharge lamp according to the present invention introduces new design parameters not only for the electrodes but also for the shape of the discharge lamp. That is, one preferred embodiment of the high-pressure discharge lamp according to the present invention has a ratio between the inner diameter d _in and the outer diameter d _out of the electrode:

It is in the range of. Either the wall or the hole acts as the cathode. As an example, a tubular electrode having a diameter of 1000 μm and an inner diameter of 350 μm has a suitable wall thickness of 350 μm. When the inner diameter is 100 μm, the thickness of the wall portion is 450 μm. When the inner diameter is 800 μm, the thickness of the wall portion is 100 μm.

  Tubular electrode prototypes were made and tested in a 250 W ceramic discharge metal halide lamp (so-called CDM lamp). The experimental results show that the high-pressure discharge lamp having the tubular electrode according to the present invention performs as expected. In particular, all discharge lamps produced an ignition at the electrode tip. In addition, the spike at the time of reignition was low, and the ignition and relaying proceeded smoothly. Furthermore, the high pressure discharge lamp with tubular electrodes according to the present invention was operated in steady state conditions at a relatively low 1.3 A current instead of the usual 2.5 A. It has also been found that the discharge lamp exhibits sufficient performance under such conditions. By observing the lit discharge lamp, it was concluded that the arc was at the electrode tip in the anode phase and moved to the inside of the wall in the cathode phase.

  These and other aspects of the invention will be apparent with reference to the embodiments described below. The accompanying drawings are for illustrative purposes only and are not drawn to scale. In particular, some dimensions are shown strongly exaggerated for clarity. Similar elements in the figures are denoted by the same reference numerals as much as possible.

  FIG. 1A is a very schematic view of a high-pressure discharge lamp according to the present invention. In this figure, the discharge vessel 10 is cut and removed. The discharge vessel 10 has a ceramic wall that encloses the discharge space 11. The discharge space 11 contains an ionizable filling material. This ionizable packing material includes not only mercury but also halides of Na, Ca and Tl in the illustrated example. The discharge vessel 10 is provided with a first neck 2 and a second neck 3, through which the first current supply conductor 4 and the second current are passed. Each supply conductor 5 extends to a pair of electrodes 6 and 7 disposed in the discharge space 11. Each of the electrodes 6 and 7 contains tungsten (W) and has a tubular shape over the entire length. The configuration of the discharge vessel itself is known.

  In the example of FIG. 1A, one end of the discharge vessel is surrounded by an outer bulb 1 having a lamp base 2. During operation of the high pressure discharge lamp, a discharge occurs between the electrodes 6 and 7. The electrode 6 is connected to a first electrical contact portion that forms a part of the lamp base portion 2 through a conductive wire 8. The electrode 7 is connected to a second electrical contact portion that forms a part of the lamp base portion 2 through a conductive wire 9. In the example of FIG. 1A, these electrodes do not have a coil in the discharge space. This has the advantage that the manufacture of the electrode is relatively simple. In addition, there is no problem of the coil fusing to the electrode during the life of the lamp, which may occur in known discharge lamps. This fusing problem thereby shifts the electrode behavior into an undesirable temperature range, leading to (early) defects in known discharge lamps or a substantial reduction in lamp performance.

In one practical embodiment of the high-pressure discharge lamp according to the invention as shown in this figure, the nominal power of the lamp is 70 W and the nominal lamp voltage is 90V. The translucent wall of the discharge vessel has a thickness of about 0.8 mm. The inner diameter of the discharge vessel is about 6.85 mm, and the distance between the electrode tips is about 7 mm. In the example of FIGS. 1A and 1B, the ionizable packing material of the lamp includes 4.6 mg of mercury and 7 mg of (Na + Tl + Ca) iodide, the molar composition ratio of the latter iodide being the total iodide content. Na is 64 mol%, Tl is 5 mol%, and Ca is 31 mol% with respect to the molar amount. The discharge vessel further contains Ar with a filling pressure of 300 mbar as a starting accelerator. During lamp operation, T _kp is 1265K. This lamp emits light with a luminous efficiency of 90 lm / W for 100 hours. The color temperature _Tc of the emitted light is 3150K. The overall color rendering coefficient _Ra is about 90.

  FIG. 1B is a cross-sectional view of a detailed portion of the high-pressure discharge lamp shown in FIG. 1A. Only the second cervical portion indicated by reference numeral 3 is shown, and the second current supply conductor 5 passes through the second cervical portion 3 and is tubular in the discharge space 11. It extends to the electrode 7. Preferably, the current supply conductor 5 is made of niobium. A rod 15 made of molybdenum or cermet is provided between the current supply conductor 5 and the tubular electrode 7. The neck portion 3 surrounds the vicinity of the tubular electrode 5 and the Mo rod 15 with a gap. A fused ceramic joint 21 is applied between the current supply conductor 5, the Mo rod 15, and the wall of the neck 3, thereby providing a hermetic seal of the discharge space 13 of the discharge vessel 10. It has been.

  FIG. 2 is a diagram schematically showing one modified embodiment of the high-pressure discharge lamp according to the present invention. Only the second neck, indicated by reference numeral 3, is shown. In this embodiment of the high-pressure discharge lamp according to the invention, the electrode 7 extends to the outside of the discharge vessel 10. In addition, in the embodiment of FIG. 2, the electrode 7 is partially filled with a rod 11 coupled to the side of the electrode 7 opposite to the discharge space 13. This solid rod 11 is preferably made of Mo, W or Rh. Molybdenum is a very suitable material because it is inexpensive and has very good resistance to the iodide atmosphere in the discharge vessel.

  In one modified embodiment (not shown in FIG. 2) of the high-pressure discharge lamp according to the invention, the rod 11 extends into the discharge space 13. In yet another alternative embodiment (not shown in FIG. 2), the rod 11 is projected from the tubular electrode 7 in the discharge space 13.

の範囲内とされる。 The novel design of the electrodes in the high-pressure discharge lamp according to the present invention introduces new design parameters not only for the electrodes but also for the shape of the discharge lamp. 1B and 2 show the inner diameter d _in and the outer diameter d _out of the tubular electrode 7. In addition, the inner diameter d _{nsp of the neck} 3 is also shown in FIGS. 1B and 2. Preferably, the ratio between the inner diameter d _in and the outer diameter d _out of the tubular electrodes 6 and 7 is

Within the range of

  Preferably, the inner diameter of the tubular electrodes 6 and 7 is at least 20 μm. Another preferable lower limit of the inner diameter is 50 μm.

の範囲内にある。 Since no coil is attached to the tubular electrode 7, the diameter of the necks 3 and 4 can be made considerably smaller than the diameter in known high-pressure discharge lamps. There must be a gap between part of the electrode (including not only tungsten but also molybdenum) and the inner wall of the burner's neck (also called “vup”) . This gap is determined by the coefficient of thermal expansion and technical tolerances. Since the rods and coils must pass through the necks 3 and 4, the inner diameter of the necks 3 and 4 is larger than the required inner diameter, usually mostly filled with molybdenum feedthroughs. Yes. If the holes in the neck can be made substantially smaller than the holes in known discharge lamps, an advantage is obtained because the volume filled with salt is also substantially reduced. Preferably, the ratio of the outer diameter d _out of the tubular electrodes 6 and 7 to the inner diameter d _nsp of the _necks 3 and 4 is

It is in the range.

  One advantage of using smaller necks 3 and 4 is that less salt can be used in the high pressure discharge lamp. In particular, it is feasible to advantageously reduce up to 80% of the salt contained in the discharge vessel 10.

の範囲内にあることを特徴とする。 One preferred embodiment of the high-pressure discharge lamp according to the invention is that the ratio between the current I _mhl of the high-pressure discharge lamp and the outer diameter d _out of the electrodes 6 and 7 is

It is in the range of.

により決定されると推測される（たとえば、タングステンについては４．５ｅＶ）。既知の電極ロッドのサイズは、陽極相におけるパワーにより左右される。電極先端の温度は、上限を３２００Ｋ、下限を２２００Ｋとし、同じ電流密度を仮定することにより計算することができる。こうして、高圧放電ランプの電流Ｉ_ｍｈｌと、電極６および７の外径ｄ_ｏｕｔとの間の比について、上記の関係が得られる。 In the above equation, the current is expressed in amperes and the diameter is expressed in millimeters. While not intending to follow any particular theory, the power P _nanode in the anode phase, which affects the temperature at the electrode tip, is

(For example, 4.5 eV for tungsten). The size of the known electrode rod depends on the power in the anode phase. The temperature of the electrode tip can be calculated by assuming the same current density with an upper limit of 3200K and a lower limit of 2200K. Thus, the above relationship is obtained for the ratio between the current I _mhl of the high pressure discharge lamp and the outer diameter d _out of the electrodes 6 and 7.

For a 250 W high pressure discharge lamp, an example of a suitable outer diameter d _out of the tubular electrode is about 680 μm. An example of a suitable thickness for the wall of the tubular electrode is about 140 μm. An example of a suitable inner diameter d _{nsp for} the necks 3 and 4 is an inner diameter in the range of about 830 to 880 μm. A conventional rod electrode of a known 250 W high pressure discharge lamp with a similar wattage has a diameter of about 800 μm. Usually, a coil having a wire thickness of 250 μm is wound around the rod, and the total diameter of the rod and the coil is 1300 μm. Thereby, it is usually necessary to set the inner diameter d _{nsp of the} neck portion to about 1500 μm. The salt reduction in this discharge lamp according to the invention compared to known discharge lamps is in the range of 50% to 70%.

Another example of a 70 W high pressure discharge lamp has an outer diameter of about 415 μm as a suitable outer diameter d _out of the tubular electrode. An example of a suitable thickness for the wall of the tubular electrode is about 85 μm. An example of a suitable inner diameter d _{nsp for} the necks 3 and 4 is about _{550 μm} . A conventional rod electrode of a known 70 W high pressure discharge lamp with a similar wattage has a diameter of about 300 μm. Usually, a coil having a wire thickness of 170 μm is wound around the rod, and the total diameter of the rod and the coil is 650 μm. Thus, it is usually necessary to set the inner diameter d _{nsp of the} neck portion to about 775 μm. The salt reduction in this discharge lamp according to the invention compared to the known discharge lamp is in the range of 30% to 50%.

Yet another example of a 35 W high pressure discharge lamp has an outer diameter of about 300 μm as a suitable outer diameter d _out of the tubular electrode. An example of a suitable thickness for the wall of the tubular electrode is about 60 μm. An example of a suitable inner diameter d _{nsp for} the necks 3 and 4 is about 435 μm. A conventional rod electrode of a known 35 W high pressure discharge lamp with similar wattage has a diameter of about 200 μm. Usually, a coil having a wire thickness of 125 μm is wound around the rod, and the total diameter of the rod and the coil is 450 μm. Thus, it is usually necessary to set the inner diameter d _{nsp of the} neck portion to about 585 μm. The salt reduction in this discharge lamp according to the invention compared to the known discharge lamp is in the range of 30% to 50%.

  In general, almost all known high-pressure discharge lamps have a typical form of electrode in which a tungsten coil is wound around a tungsten rod. The coil is fused to the rod or tightened tightly to the rod. The coil has a great influence on the behavior at start-up and the cathode phase (reignition peak) in the steady state. The coil also improves ignition and relay behavior by providing a spot where the arc can easily connect to the coil. This improvement in behavior can be attributed to three factors. First, during ignition, the electric field is distorted by deformations, which, in combination with the charge on the wall, facilitates ignition. Second, because of its low mass and lower thermal conductivity, the coil reaches a higher temperature faster than the rod (the contact from the coil to the rod is a point-line contact and therefore higher heat With resistance). Third, the arc appears to connect between the two turns of the coil.

  Many drawbacks are known for the conventional rod + coil configuration. Since the thermal contact between the coil and the rod and the position of the coil relative to the tip of the rod are variables that are difficult to control, one difficulty is how to make a replicaable electrode. It is. In addition, the wire end of the coil affects the behavior of the electrode. If the wire end protrudes from the rod, the arc is connected to the wire end and the coil wire reaches a high temperature and melts so as to flow backward. During the life of the lamp, the coil may fuse to the rod, thereby shifting the electrode behavior to an undesirable temperature range. This leads to lamp defects or significant performance degradation.

  According to the invention, tungsten tubular electrodes are used. The hole in the tube functions as a cathode. That is, this tubular electrode is in principle an electrode made from one element, and the hole size determines the cathode function, and the amount of tungsten per millimeter determines the anode function. Since ignition occurs from the tip of one electrode to the tip of the adjacent electrode, there is an additional advantage when starting the high pressure discharge lamp. It has been observed that the arc connects to the hole portion rather than to other portions of the tubular electrode. In this way, the arc connection does not move during the run-up and only supplies power to the top, as is desirable. In the high-pressure discharge lamp according to the present invention, sputtering is greatly reduced, and glow-arc transition is minimized. This has an advantageous effect on the life and maintainability of the discharge lamp according to the present invention.

  The embodiments described above are intended to be illustrative and not limiting of the present invention, and those skilled in the art will recognize many modified embodiments without departing from the scope of the invention as claimed. Note that it could be designed. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “comprising” and their conjugations do not exclude the presence of elements or steps other than those listed in a claim. The word “one” preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by hardware with several distinct elements, or by a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same hardware element. The mere fact that certain measures are recited in mutually different dependent claims does not imply that a combination of these measures cannot be used effectively.

The figure which showed one Embodiment of the high pressure discharge lamp which concerns on this invention Detailed partial view of the high-pressure discharge lamp shown in FIG. 1A The figure which showed one modified embodiment of the high pressure discharge lamp which concerns on this invention

Claims (10)

A discharge vessel enclosing a discharge space containing an ionizable filling material;
The discharge vessel has a first and second neck portions facing each other, provided with a pair of electrodes arranged in the discharge space;
Each of the electrodes is tubular over its entire length.   The high-pressure discharge lamp according to claim 1, wherein the electrode does not have a coil in the discharge space.   The high-pressure discharge lamp according to claim 1 or 2, wherein the electrode extends to the outside of the discharge vessel.   4. The high-pressure discharge lamp according to claim 3, wherein each of the electrodes is partially filled with a rod coupled to a side of the electrode opposite to the discharge space.   The high pressure discharge lamp according to claim 4, wherein the rod extends into the discharge space. The ratio between the inner diameter d _in and the outer diameter d _out of the electrode is

The high-pressure discharge lamp according to claim 1 or 2, wherein the high-pressure discharge lamp is within the range.   The high-pressure discharge lamp according to claim 1 or 2, wherein the tubular electrode has an inner diameter of at least 20 µm. The ratio between the outer diameter d _out of the tubular electrode and the inner diameter d _nsp of the _neck is:

The high pressure discharge lamp according to claim 2, wherein the high pressure discharge lamp is within the range.   3. The high pressure discharge lamp according to claim 1, wherein the electrode is made of tungsten. The ratio between the current I _mhl of the high pressure discharge lamp expressed in amperes and the outer diameter d _{out of the} electrode expressed in millimeters is

The high-pressure discharge lamp according to claim 1 or 2, wherein the high-pressure discharge lamp is within the range.

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